Devices including an optical area sensor (imager) and an entrance pupil are used, for example, as front cameras in vehicles. In this case, the device is situated in an area with respect to a longitudinal axis of the vehicle behind a windshield of the vehicle in such a way that the optical semiaxis crosses the windshield and the device thus visually records a wider area with respect to the longitudinal axis in front of the windshield of the vehicle and in particular ahead of the vehicle.
An aperture angle is defined by an extension of the surface sensor and a distance between the area sensor and the entrance pupil. The device may in addition include one or multiple imaging optical system(s).
The recorded images and/or videos may be used in diverse ways. They may be displayed, for example, on a screen for supporting the driver, and/or they may be evaluated automatically, for example, by a driver assistance system, which determines the distance to a preceding vehicle.
Vehicles are described in an axis system, a longitudinal axis extending horizontally and in parallel to a direction of travel of the vehicle, and a vertical axis extending vertically. A transverse axis extends perpendicularly to the longitudinal axis and perpendicularly to the vertical axis. The transverse and longitudinal axes define a horizontal plane, to which the windshield is inclined at an angle differing from 0° and 90°, 360° corresponding to the complete circle. The inclination may vary along the vertical axis and/or along the transverse axis.
A distance of the device from the windshield and the aperture angle determine a field of vision of the windshield, through which the device “sees,” and which must therefore be transparent if the full aperture angle is to be utilized.
The device may be accommodated, for example, in the foot of a center rear view mirror, it being possible for the foot to be attached to the windshield. The windshield area in which the foot is attached may partially include so-called black print. However, the field of vision must be kept free from black print if the full aperture angle is to be utilized.
It is desirable to design the field of vision to be as small as possible to minimize the visibility of the device from the outside, to reduce the effect of the windshield as an enlarging ancillary lens and/or to maximize the black print.
If the full aperture angle is to be utilized, this may occur, for example, by reducing the distance of the device from the windshield. However, a structural dimension of the device requires a minimum distance. Furthermore, it is possible to minimize the angle between the optical semiaxis and a normal of the windshield. However, it is desirable to keep the optical axis parallel to the horizontal plane of the vehicle. However, the optical semiaxis of the area sensor then crosses the windshield in such a way that it is inclined in relation to a normal of the windshield corresponding to the inclination.
If the device having a horizontal optical semiaxis is situated at the minimum distance to the windshield, this also causes the field of vision to be further reduced in that an optical element is situated between the device and the windshield. Thus DE 10 2008 0270 307 A1 describes an optical element in the form of a prism system, which has at least two prisms made from transparent materials situated one behind the other, the prisms being oriented in such a way that they have opposite refraction directions and their surfaces facing one another do not extend in parallel to one another. US 2003/0010890 A1 concerns a glass block which is introduced in front of a camera at an angle.